US20080217372A1 - Fastener Driving Tool - Google Patents

Abstract

A fastener driving tool comprising a tool nose through which a fastener is fired and a loading apparatus for introducing the fastener into the tool nose. The fastener is propelled by a gas combustion mechanism comprising a first priming cylinder having a first piston and an air intake fluidically connected via a first valve apparatus to a second delivery cylinder having a second piston. The first priming cylinder is fluidically connected to a fuel gas reservoir via a second valve apparatus. The first priming cylinder receives fuel from the reservoir and air through the air intake to form an air/fuel gas mixture therein. The first piston compresses the air/fuel gas mixture and transfers the air/fuel gas mixture to the second delivery cylinder via the first valve apparatus. The air/fuel mixture is ignited therein and urges the second piston towards the fastener and propels the fastener away from the tool nose.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a National Stage application of International Application No. PCT/AU2004/001836, filed on Dec. 30, 2004, which claims priority of Australian application number 2003907160, filed on Dec. 30, 2003 and Australian application number 2004900539, filed on Feb. 4, 2004.
BACKGROUND OF THE INVENTIONField of the Invention
• The present invention relates to an internal combustion fastener driving tool.
• Fastener driving tools have been developed that use internal combustion as a power source to drive fasteners, such as nails, into a work piece or substrate. The tools ignite a fuel/air mixture in a combustion chamber to forcibly drive a piston, which then ejects the fastener from the tool. The effectiveness of the prior art tools is largely limited by their efficiency in rapidly igniting the complete volume of fuel/air mixture. If insufficient volumes of fuel ignite, the device delivers unsuitable driving forces to the fastener. If the tool produces unreliable power outputs, the fasteners may be driven to unsatisfactory depths or insufficiently seated. Prior art devices in the past have attempted to address these inefficiencies by making a larger tool and wasting larger volumes of fuel.
• One such prior art device is described in U.S. Pat. No. 5,213,247 (Gschwend et al). This device describes a network of mechanisms that operate to measure a specific quantity of fuel and then draw that fuel, along with air, into a combustion chamber by mechanically expanding the combustion chamber volume. A drawback of this device is that the fuel and gas are not mixed sufficiently, which decreases the efficiency of combustion. Secondly, the device draws fuel and air into the combustion chamber with a partial vacuum. As a consequence, the fuel/air mixture is ignited at a low pressure, which leads to a low burn rate and further inefficiency. This is particularly problematic in that the less efficient an internal combustion fastener driving tool is, the more susceptible the device is to output fluctuations that result in ignition failures and unsatisfactory driving forces to the fastener.
• The present invention seeks to provide a fastener driving tool that will ameliorate or overcome at least one of the deficiencies of the prior art.
SUMMARY OF INVENTION
• In a first aspect the present invention consists in a fastener driving tool comprising: a tool nose through which a fastener is fired; loading means for introducing said fastener into said tool nose; said fastener being adapted to be propelled by a gas combustion mechanism, wherein said gas combustion mechanism comprises a first priming cylinder having a first piston and an air intake fluidically connected via a first valve means to a second delivery cylinder having a second piston, said first priming cylinder fluidically connected to a fuel gas reservoir via a second valve means, said first priming cylinder adapted to receive fuel gas from said fuel gas reservoir and air through said air intake thereby forming an air/fuel gas mixture therein, said first piston adapted to compress said air/fuel gas mixture and transfer said air/fuel gas mixture to said second delivery cylinder via said first valve means, said air/fuel mixture ignited therein and thereby urging said second piston towards said fastener and propelling the same away from said tool nose.
• Preferably in a first embodiment said first piston is mechanically actuated. Preferably said second valve means is opened and closed via mechanical actuation.
• Preferably in a second embodiment said first piston is electromagnetically actuated. Preferably said second valve means is opened and closed via electromagnetic actuation.
• Preferably said fastener driving tool is a nail gun.
• Preferably in a third embodiment a mechanism movable between a first and a second position along said tool nose includes a latching means for engaging said second position, such that said air/fuel gas mixture is further compressed by said second piston as said mechanism is moved from said first to said second position with said latching means engaged and wherein the downward force from the ignition of said air/fuel mixture overcomes said latching means and urges said second piston towards said fastener.
• Preferably a bumper is disposed near the bottom of said second delivery cylinder, such bumper adapted to be compressed by said second piston in the bottom of its travel and wherein the subsequent restoration of said bumper is further adapted to forcibly return said second piston back up said second delivery cylinder.
• Preferably the interior of said bumper forms a chamber adapted to port pressurised air via an outlet valve through a transfer channel to said first priming cylinder as said bumper is compressed.
• Preferably said first piston has an internal receiver for storing said pressurised air.
• Preferably a sealing ring having a semi-flexible lip is disposed around the periphery of said second piston.
• Preferably a mixing fan is rotatably mounted to the interior of said second delivery cylinder.
• Preferably an externally mounted motor drives said mixing fan via magnetic coupling.
• Preferably said second delivery cylinder is exhausted via a plate valve that fluidly connects said second delivery cylinder with an exhaust plenum when said plate valve is opened.
• Preferably in a second aspect the present invention consists in an apparatus utilising a gas combustion mechanism for propulsion of an object, said gas combustion mechanism comprises a first priming cylinder having a first piston and an air intake fluidically connected via a first valve means to a second delivery cylinder having a second piston, said first priming cylinder fluidically connected to a fuel gas reservoir via a second valve means, said first priming cylinder adapted to receive fuel gas from said fuel gas reservoir and air through said air intake thereby forming an air/fuel gas mixture therein, said first piston adapted to compress said air/fuel gas mixture and transfer said air/fuel gas mixture to said second delivery cylinder via said first valve means, said air/fuel mixture ignited therein and thereby urging said second piston towards said object thereby propelling the same.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective schematic view of a first embodiment of a nail gun in accordance with the fastener driving tool of the present invention.
• FIG. 2 is a cross-sectional schematic view of the nail gun ofFIG. 1.
• FIG. 3 is a cut away end view of the nail gun ofFIG. 1.
• FIG. 4 is an enlarged view of the gas combustion mechanism shown inFIG. 2.
• FIG. 5 is an enlarged view of the gas combustion mechanism shown inFIG. 2, as air and fuel enter the priming cylinder.
• FIG. 6 is an enlarged view of the gas combustion mechanism shown inFIG. 2, as air/fuel mixture is compressed in the priming cylinder.
• FIG. 7 is an enlarged view of the gas combustion mechanism shown inFIG. 2, as air/fuel mixture is transferred from the priming cylinder to the driving cylinder.
• FIG. 8 is an enlarged view of the gas combustion mechanism shown inFIG. 2, as air/fuel mixture within the driving cylinder is compressed.
• FIG. 9 is an enlarged view of the gas combustion mechanism shown inFIG. 2, as the ignited air/fuel mixture displaces the piston within the driving cylinder towards the nail to be fired.
• FIG. 10 is an enlarged view of the gas combustion mechanism shown inFIG. 2, as the driver connected to the piston propels the nail and the gas begins to be exhausted from the driving cylinder.
• FIGS. 11 and 12 are enlarged views of the gas combustion mechanism shown inFIG. 2, as piston is returned back up the driving cylinder and remaining exhaust gas is purged from the driving cylinder.
• FIG. 13 is an enlarged view of the cycle wheel arrangement used to control the tool cycle.
• FIG. 14 is an enlarged view of an alternative embodiment of the cycle wheel arrangement shown inFIG. 13.
• FIGS. 15aand15bare enlarged elevation and cutaway views of the fuel gas cartridges.
• FIG. 16 is a cross-sectional schematic view of a second embodiment of a nail gun in accordance with the fastener driving tool of the present invention.
• FIG. 17 is a schematic view of a third embodiment of a nail gun in accordance with the fastener driving tool of the present invention.
• FIG. 18 is an enlarged schematic view of the internal receiver of the nail gun depicted inFIG. 17.
• FIG. 19 is an enlarged cutaway partial view of the sealing ring of the nail gun depicted inFIG. 17.
• FIG. 20 is an enlarged schematic view of the plate valve ofFIG. 17.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
• FIGS. 1 and 2 depict a combustion driven nail gun (tool) for firing nail fasteners. The nail gun comprises a priming cylinder A and a power driving cylinder B, housed within toolmain body casing62. A tool support handle7 having a pistol grip5 extends fromcasing62 and houses a fuel gas cartridge (reservoir)3. A battery1 housed withinremovable battery casing2 is attached to support handle7. A nail fastener cartridge (or magazine)4 deliversnail fasteners8 to tool nose (or barrel)9.
• The operation of the combustion nail gun will now be described. A user holds the combustion driven nail gun by tool support handle7 and pistol grip5. The user's finger is placed onfiring trigger16. Primarymicro trigger15 is activated. Electronic central processing unit (CPU)18 is alerted that the tool is in operation.CPU18 switches circuit on to a priming cylinder drive having acycle sensor wheel21 and main power feed slip ring66 as shown inFIG. 13.Motor35 is activated.Wheel21 rotates causingfirst piston24 to progress downward in priming cylinder A via connecting rod23, crank pin22 and bearing34. A partial vacuum occurs abovepiston24 in priming cylinder A causingtransfer valve32 to close andintake valve31 to open. Air is drawn into priming cylinder A throughintake port30. Fueldelivery striker segment25 makes contact withpin27opening gas valve26 in the head ofgas cylinder3 for a short duration. A given volume of atomised fuel is released fromcylinder3 and passes throughgallery28 tointake port30. Atomised fuel gas mixes with inward flowing air atintake port30 throughvalve31, filling priming cylinder A with a mixture of fuel, gas and air, seeFIG. 5.Piston24 progresses back up priming cylinder A, and a pressure rise occurs closingvalve31, seeFIG. 6, and openingvalve32 transferring air/fuel mixture from priming cylinder A into driving cylinder B. Electromagnetic exhaust valves42 and45 are energised during the upward progression ofpiston24 causingvalve head45 to open, allowing the inward flow of fuel/gas air mixture throughvalve32 to purge residual exhaust gases from combustion space in cylinder B, seeFIG. 7. When 50% of the fuel/gas air mixture phase has takenplace slip ring67 disengages electromagnetic valve42 causingvalve head45 to close via a coil spring (not shown) and sealingexhaust port43.Piston24 progresses to the top of priming cylinder A transferring fuel/gas air mixture into combustion area of driving cylinderB. Slip ring69 disengages power circuit to motor.CPU18 switches circuit on to coolingfan motor41. Tool is positioned and pressed onto a work piece,mechanism61 is depressed alertingCPU18 tool is safe to fire.CPU18 switches circuit on to switchmechanism17 allowingmain firing trigger16 to be fully depressed.Mechanism17alerts CPU18 to activateigniter48. Fuel/air mixture in combustion area of driving cylinder B ignites and an explosion occurs, a rapid rise of pressure occurs causingvalve32 to seal close, seeFIG. 8.Second piston51 anddriver55 progress down bore54 ofcylinder B. Driver55drives fastener8 down tool nose9 into the work piece. Aspiston51 progresses down cylinder B air underpiston51 escapes throughexhaust port60 and12. Whenpiston51 has traveled 90% of its travel the under side ofpiston51 comes into contact withrubber bumper58.Bumper58 absorbs energy and slows the progression ofpiston51.Exhaust port60 is then uncovered allowing exhaust gases to escape from cylinder B into cavity57 and then out through toolhousing exhaust port13. At the end oftravel piston51,piston51 makes contact with power driver cylinder piston end ofstroke sensor59.Sensor59alerts CPU18 of the position ofpiston51.CPU18 energises electromagnetic exhaust valve42 to open allowing exhaust gases to be expelled from the top of cylinder B throughexhaust port43 into cavity57 and out throughcavity13. Stored energy inbumper58returns piston51 anddriver55 back up bore54 in driving cylinder B. Remaining exhaust gases in driving cylinder B are purged throughexhaust port43. Air is allowed to be displaced to the underside ofpiston51 in cylinder B throughexhaust port60 and12 to prevent a partial vacuum inhibiting the return ofpiston51 to top ofbore54 in cylinder B, seeFIGS. 11 and 12.CPU18 has an electronic timing mechanism built-in to operate electromagnetic valve42 and coolingfan41. Whenpiston51 has reached the top ofbore54 of cylinder B, theCPU18 switches the circuit to electromagnetic exhaust valve42 off, allowingvalve head45 to close.CPU18 allows coolingfan41 to remain active for a period of approximately 10 seconds in one-shot use only, or for continuous application the coolingfan41 may remain active. A temperature sensor (not shown) in cavity57 in communication withCPU18 may be incorporated.
• FIG. 13 depicts a mechanical brake/limiting mechanism (not shown) to ensure that only one revolution ofcycle wheel21 per tool cycle is required.
• FIG. 14 is an alternate embodiment to themechanical mechanism21 ofFIG. 13. In this alternate embodiment electronic crank angle mechanisms70,19a,stepper motor35 and high-tension spark mechanisms maybe incorporated into and in communication withCPU18.
• FIG. 15 depicts high pressure liquid fuel cylinders containing for example methanol as a fuel medium and liquid/gaseous CO₂as a pressurizing medium as opposed to a conventional MAPP gas. Storing fuel in this matter typically at 850 psi allows more efficient atomization of the fuel gas medium and combining with air mass in a combustion cylinder process more energy is extracted. Hydrogen may also be utilised as a fuel gas medium.
• FIG. 16 depicts a second embodiment of a nail gun in accordance with the present invention. The nail gun of this second embodiment is similar to that of the first embodiment and like reference numerals have been used to depict similar components. The main difference is that the first embodiment shown inFIG. 2 has an actuation mechanism in the form of a connecting rod23, crank pin22 and bearing34 for mechanically actuating thepiston24 within priming cylinder A. However, in this second embodiment the actuation mechanism is replaced by an electromagnetic actuation mechanism. A solenoid cylinder (or coil)102 actuatespiston24 to transfer gas/fuel air mixture into driving cylinder B. Apiston return spring103 is connected topiston24 to urge the piston upwardly whensolenoid cylinder102 is deactivated. Furthermore,gas release solenoid104 replaces the mechanical means (of the first embodiment) of fuel delivery tointake port30. The priming cylinder A also hasexhaust ports105.Solenoids102 and104 are both in communication withCPU18 and are both electronically actuated.
• FIG. 17 depicts a third embodiment of a nail gun in accordance with the present invention. This embodiment is similar to that of the previous embodiments and like reference numerals have been used to denote similar components. This embodiment shows a number of preferable features, each of which may replace or compliment corresponding components of the previous embodiments. The preferable features are described individually in the following paragraphs.
• The nail gun depicted inFIG. 17 comprises first and second springbiased balls201 and202 that are disposed onmechanism61 and engage the bottom ofdriver55 to retainsecond piston51 near the top of drivingcylinder B. Balls201 and202 move inwardly towards each other by spring force, oncedriver55 passes above them on the return stroke of the tool. In alternative arrangements,balls201 and202 engage location indentations indriver55, which advantageously provides positive control ofdriver55. In use,balls201 and202 retainsecond piston51 anddriver55 high in driving cylinder B, even as the compressed fuel/air gas mixture is introduced. When the tool is subsequently positioned and pressed onto the work piece,mechanism61 is depressed from a first to a second position, alertingCPU18 that the tool is safe to fire. Asmechanism61 is depressed,second piston51 also moves higher, further compressing the air/fuel gas mixture in driving cylinder B just prior to ignition. Upon ignition,second piston51 anddriver55 are forcibly driven down, overcoming the spring force of first and second spring biasedball201 and202. Whensecond piston51 anddriver55 complete their return stroke, first and second springbiased balls201 and202 again engage the bottom ofdriver55. This arrangement enables high pre-ignition gas pressures to be achieved due to the extra 10% or so of upward travel imparted tosecond piston51.
• The third embodiment of the nail gun depicted inFIG. 17 depicts achamber203 that exists in the interior ofbumper58.Bumper58 is preferably constructed of high-grade durable rubber and layered fabric to provide durability and high resilience. In this configuration,bumper58 still slows the progression ofpiston51 and then returnspiston51 anddriver55 back up bore54 in driving cylinder B. For those purposes, a spring may also supplementbumper58. In use, asbumper58 is compressed bypiston51,chamber203 compresses, sending pressurised air outoutlet valve204, throughtransfer channel205 and intointernal receiver206 ofpiston24.Bumper58 andchamber203 resiliently restore from their compressed state, forcibly returningpiston51 back up bore54. The expanding volume ofchamber203 causes a pressure drop that closesoutlet valve204 and opens fillvalve209, drawing fresh air intochamber203 while sealingtransfer channel205 at pressure. In this way, wasted energy is recovered by pumping pressurised air back to priming cylinder A for subsequent use. The pressure of the air/fuel mixture is also increased, which in turn increases the efficiency of its combustion.
• FIG. 18 will now be used to describe howpiston24 andinternal receiver206 interact to utilise the air pressurised bychamber203. The motion ofpiston24 occurs as explained in the previous embodiments. Wheneverpiston24 is at the top of priming cylinder A,inlet aperture207 is aligned withtransfer channel205.Piston24 is in this top position when the downward motion ofpiston51compresses bumper58 and thus pressurises the air intransfer channel205 through tointernal receiver206. As explained above, whenpiston51 returns up bore54,outlet valve204 closes, keepingtransfer channel205 andinternal receiver206 pressurised. Upon the next use,piston24 travels downward, sealinginternal receiver206. The same downward motion simultaneously creates a partial vacuum abovepiston24 in priming cylinder A, causingtransfer valve32 to close andintake valve31 to open. Air and fuel are drawn into priming cylinder A throughintake port30 andvalve31. Whenpiston24 nears the bottom of its travel, bypass208 aligns withbypass aperture210 allowing pressurised air frominternal receiver206 to pressurise the air/fuel mixture abovepiston24. The consequential pressure rise closesintake valve31.Piston24 then progresses back up priming cylinder A and a further pressure rise occurs, openingvalve32 and transferring the air/fuel mixture from priming cylinder A into driving cylinder B. This arrangement advantageously allows the pressurised air fromchamber203 to be stored for use at a later time.
• FIG. 19 is an enlarged partial view ofsecond piston51 depicting a preferable configuration of sealingring52. In this configuration, sealingring52 is fabricated from carbon impregnated Teflon and has the cross-sectional shape shown inFIG. 19. The material of sealingring52 and its small contact area withbore54 results in minimal frictional resistance, which advantageously results in a smaller upward force required to returnsecond piston51 back up driving cylinder B. A semiflexible lip211 extends upward from sealingring52 and is spaced apart frombore54 whenlip211 is at rest. Upon ignition, high pressure acts on the top ofsecond piston51 and sealingring52, causinglip211 to flex outward against bore54 from its rest position, thereby providing a greater gas seal and minimising losses. Once the gas pressure is relieved, the sealinglip211 returns to its rest position off ofbore54 thus minimising resistance during the return stroke.
• FIG. 20 is an enlarged schematic view of a preferable alternative configuration of powerdriver cylinder head47. In this configuration, mixingfan212 is rotatably mounted to the interior of power driving cylinderB. Mixing fan212 is magnetically coupled to coolingfan motor41, which is mounted to the exterior of driving cylinder B. Structural components between mixingfan212 and coolingfan motor41 are preferably made of aluminium. Mixingfan212 agitates the air/fuel gas mixtures to obtain more complete combustion, raising the reliability of the tool's power output.
• FIG. 20 also depicts electromagnetic valve42 being replaced by plate valve213, which is preferably also electro magnetically actuated. Whenplate valve coil215 is de-energised,plate valve spring214 biases plate valve213 to the open position. WhenCPU18 energisesplate valve coil215, electro magnetic force overcomesplate valve spring214 to close plate valve213. When plate valve213 is open, power driving cylinder B is in fluid communication withexhaust plenum216, allowing rapid purging of residual exhaust gases from the combustion space in cylinder B.
• Whilst the abovementioned embodiment of the present invention is described with reference to a nail gun for driving nails, it should be understood that the present invention in other not shown embodiments can be used to fire other fasteners, but is limited thereto. Also, in other not shown embodiments the gas combustion mechanism of the abovementioned embodiment may be used in some other apparatus where an object is propelled. Such drive apparatus may have a tool or drive application different to the nail gun of the abovementioned embodiments.
• The term “comprising” (and its grammatical variations) as used herein is used in the inclusive sense of “having” or “including” and not in the exclusive sense of “consisting only of”.

Claims (15)

1. A fastener driving tool comprising: a tool nose through which a fastener is fired; a loading apparatus for introducing said fastener into said tool nose; said fastener being propellable by a gas combustion mechanism, wherein said gas combustion mechanism comprises a first priming cylinder having a first piston, an air intake and a first valve apparatus for fluidically connecting said air intake to a second delivery cylinder having a second piston, said first priming cylinder fluidically connected to a fuel gas reservoir via a second valve apparatus, wherein said first priming cylinder receives fuel gas from said fuel gas reservoir and air through said air intake to form an air/fuel gas mixture therein, wherein said first piston compresses said air/fuel gas mixture and transfers said air/fuel gas mixture to said second delivery cylinder via said first valve apparatus, and wherein said air/fuel mixture is ignited therein and urges said second piston towards said fastener and propels said fastener away from said tool nose.

2. The fastener driving tool as claimed inclaim 1, wherein said first piston is mechanically actuated.

3. The fastener driving tool as claimed inclaim 1, wherein said second valve apparatus is opened and closed via mechanical actuation.

4. The fastener driving tool as claimed inclaim 1, wherein said first piston is electromagnetically actuated.

5. The fastener driving tool as claimed inclaim 1, wherein said second valve apparatus is opened and closed via electromagnetic actuation.

6. The fastener driving tool as claimed inclaim 1, wherein said fastener driving tool is a nail gun.

7. The fastener driving tool as claimed inclaim 1, wherein a mechanism movable between a first and a second position along said tool nose includes a latching apparatus for engaging said second position, such that said air/fuel gas mixture is further compressed by said second piston as said mechanism is moved from said first to said second position with said latching apparatus engaged and wherein the downward force from the ignition of said air/fuel mixture overcomes said latching apparatus and urges said second piston towards said fastener.

8. The fastener driving tool as claimed inclaim 1, wherein a bumper is disposed near the bottom of said second delivery cylinder, said bumper being compressible by said second piston in the bottom of the travel of said second piston and wherein the subsequent restoration of said bumper forcibly returns said second piston back up said second delivery cylinder.

9. The fastener driving tool as claimed inclaim 8, wherein the interior of said bumper forms a chamber for porting pressurised air via an outlet valve through a transfer channel to said first priming cylinder as said bumper is compressed.

10. The fastener driving tool as claimed inclaim 9, wherein said first piston has an internal receiver for storing said pressurised air.

11. The fastener driving tool as claimed inclaim 1, further comprising a sealing ring having a semi-flexible lip and being disposed around the periphery of said second piston.

12. The fastener driving tool as claimed inclaim 1, wherein a mixing fan is rotatably mounted to the interior of said second delivery cylinder.

13. The fastener driving tool as claimed inclaim 12, wherein an externally mounted motor drives said mixing fan via magnetic coupling.

14. The fastener driving tool as claimed inclaim 1, further comprising a plate valve and an exhaust plenum, wherein said plate valve fluidly connects said second delivery cylinder with said exhaust plenum when said plate valve is opened for exhausting said second delivery cylinder.

15. An apparatus utilising a gas combustion mechanism for propulsion of an object, said gas combustion mechanism comprising a first priming cylinder having a first piston and an air intake fluidically connected via a first valve apparatus to a second delivery cylinder having a second piston, said first priming cylinder fluidically connected to a fuel gas reservoir via a second valve apparatus, wherein said first priming cylinder receives fuel gas from said fuel gas reservoir and air through said air intake to form an air/fuel gas mixture therein, wherein said first piston compresses said air/fuel gas mixture and transfers said air/fuel gas mixture to said second delivery cylinder via said first valve apparatus, and wherein said air/fuel mixture is ignited therein and urges said second piston towards said object to propel said object.

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